U.S. patent number 6,504,260 [Application Number 09/787,367] was granted by the patent office on 2003-01-07 for wind turbine with counter rotating rotors.
This patent grant is currently assigned to Jeumont Industrie. Invention is credited to Yves Debleser.
United States Patent |
6,504,260 |
Debleser |
January 7, 2003 |
Wind turbine with counter rotating rotors
Abstract
A first capture unit includes a first turbine rotor having a
first hub. A second capture unit includes a second turbine rotor
having a second hub. The rotors counter-rotate independently. A
first electric generator includes a first rotor fixed to the first
turbine rotor and a first stator fixed so as to face the first
rotor. A second electric generator includes a second rotor having a
rotor fixed to the second turbine rotor and a second stator fixed
so as to face the second rotor. Power electronic means control the
electric currents produced by the first and the second stators of
the first and the second electric generators independently of each
other thus regulating the rotational speed of the first and second
turbine rotors.
Inventors: |
Debleser; Yves (Enghien
Belgique, BE) |
Assignee: |
Jeumont Industrie (Courbevoie,
FR)
|
Family
ID: |
9548426 |
Appl.
No.: |
09/787,367 |
Filed: |
March 16, 2001 |
PCT
Filed: |
July 19, 2000 |
PCT No.: |
PCT/FR00/02077 |
PCT
Pub. No.: |
WO01/07784 |
PCT
Pub. Date: |
February 01, 2001 |
Foreign Application Priority Data
|
|
|
|
|
Jul 22, 1999 [FR] |
|
|
99 09551 |
|
Current U.S.
Class: |
290/44;
290/55 |
Current CPC
Class: |
H02K
7/1838 (20130101); F03D 9/25 (20160501); F03D
7/02 (20130101); Y02E 10/72 (20130101); F03D
80/70 (20160501); Y02E 10/725 (20130101); F05B
2270/20 (20130101); Y02E 10/721 (20130101); Y02E
10/723 (20130101); F05B 2270/1013 (20130101) |
Current International
Class: |
F03D
7/00 (20060101); F03D 1/00 (20060101); F03D
1/02 (20060101); F03D 9/00 (20060101); F03D
009/00 () |
Field of
Search: |
;290/43,44,54,55 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Ponomarenko; Nicholas
Attorney, Agent or Firm: Connolly Bove Lodge & Hutz
LLP
Claims
What is claimed is:
1. A device for capturing wind energy to produce electrical energy,
comprising: a vertical mast; a nacelle mounted rotatably about a
vertical axis on the upper part of the mast; a first capture unit
including a first turbine rotor having a first hub and at least two
first blades fixed to the first hub in generally radial directions,
said first hub being mounted rotatably about a generally horizontal
axis on the nacelle; a second capture unit including a second
turbine rotor having a second hub and at least two second blades
fixed to the second hub in generally radial directions, said second
hub being mounted rotatably about the generally horizontal axis
about which said first hub is rotatably mounted so that said first
turbine rotor and said second turbine rotor rotate independently of
each other and said blades of said second rotor are oriented such
that said first rotor and said second rotor counter rotate; a first
electric generator of discoid shape including a first rotor having
one disc-shaped rotor part fixed to the first turbine rotor and a
first stator having one disc-shaped stator part fixed on the
nacelle so as to face the rotor part of the first rotor; a second
electric generator of discoid shape including a second rotor having
one disc-shaped rotor part fixed to the second turbine rotor and a
second stator having one disc-shaped stator part fixed on the
nacelle so as to face the rotor part of the second rotor; and power
electronic means for controlling the electric currents produced by
said first and said second stators of said first and said second
electric generators independently of each other thus regulating the
rotational speed of said first turbine rotor and said second
turbine rotor.
2. The wind energy capturing device of claim 1 wherein the power
electronic means regulates the rotational speed of the first and
second rotors independently of each other at an optimum value
depending on the wind speed for optimizing the energy and power
produced by the device.
3. The wind energy capturing device of claim 2 wherein the power
electronic means operates so that, in a first zone of operation A
of a plot of power supplied by said first and said second capture
units as a function of the wind speed, for wind speeds ranging from
the capture unit start-up speed to a speed at which the rotating
part of the first capture unit is aerodynamically stalled, the
first capture unit and the second capture unit are operated under
conditions of maximum efficiency, and the speed of the rotating
parts of the capture units is then regulated in order to regulate
the aerodynamic stall of the rotating part of the first capture
unit and cause the residual energy to be recovered by the rotating
part of the second capture unit, so that the increase in power and
energy produced by the second capture unit gradually reaches the
value of the power and of the energy recovered by the first capture
unit, for increasing wind speed.
4. The wind energy capturing device of claim 3 wherein the power
electronic means operates so that the increase in power and energy
produced by the second capture unit changes progressively, after
the onset of stall in the rotating part of the first capture unit,
from 50% to 100% of the power and energy produced by the first
capture unit.
Description
FIELD OF THE INVENTION
The invention relates to a device for capturing wind energy in
order to produce electrical energy.
BACKGROUND OF THE INVENTION
Devices for capturing the energy supplied by the wind, or wind
turbines, comprising a vertical mast, a nacelle mounted so that it
can rotate about a vertical axis on the upper part of the mast, and
at least one capture unit carried by the nacelle, are known. The
unit for capturing the wind energy comprises at least one turbine
rotor consisting of a hub mounted so that it can rotate on the
nacelle about an approximately horizontal axis and at least two
blades (generally two or three blades) fixed to the hub in
approximately radial directions.
The nacelle, which is generally streamlined, is oriented,
automatically or by command, in such a way that the horizontal axis
of rotation of the hub is directed into the wind and so that the
turbine rotor is rotated at a certain speed which depends on the
wind speed.
The energy recovered by the turbine rotor of the wind turbine can
be used in different ways and, in particular, this energy can be
converted into electrical energy which can be used locally at the
site of the wind turbine or sent to a distribution grid.
In this case, the capture unit of the wind turbine also constitutes
a unit for producing electrical energy and comprises an electric
generator having at least one rotor secured to the turbine rotor
and at least one stator fixed to the nacelle.
A first problem encountered in the case of units for capturing wind
energy and producing electrical energy relates to the need to make
the rotor the electric generator rotate at a sufficiently high
speed, by rotation of the turbine rotor. To achieve that, it is
generally necessary to use mechanical step-up gearing between the
turbine rotor and the generator rotor. Such a device makes the wind
turbine more complicated to construct and to maintain.
It has also been proposed for at least two turbine rotors mounted
on one and the same axis and rotating in opposite directions to one
another to be combined for driving the electric generator. In this
case, it is necessary to provide means of mechanical connection
between the two turbine rotors so as to drive and to regulate the
rotational speed of the rotor of the electric generator.
Such mechanical connection devices are complex and considerably
increase the size of the functional part of the wind turbine.
When two contra-rotating turbine rotors are used, a first turbine
rotor is directed into the wind and the second turbine rotor, which
follows on from the first turbine rotor in the direction of the
wind, uses at least some of the recoverable energy of the wind
which was not captured by the first turbine rotor.
The devices for mechanical connection between the turbine rotors do
not generally allow the two turbine rotors to operate ideally,
whatever the wind speed, that is to say do not allow operation such
that the combined energy produced over a given period, for example
over a year, is as close as possible to the maximum combined
recoverable amount of energy.
In other words, there is not yet known any means that allows the
operation of the first and of the second contra-rotating turbine
rotors to be optimized according to the wind speed.
When the wind speed increases, above and beyond the wind turbine
start-up speed, at a certain wind speed aerodynamic stall occurs or
is brought about, providing some regulation of the operation of the
wind turbine. It is necessary to provide mechanical means, for
example devices for adjusting the pitch of the blades of the
turbine rotors of the wind turbines, in order to stall or feather
the turbine rotors, that is to say bring the blades into a position
not subjected to the wind, under desired conditions. These
mechanical devices are complex and may increase the risks of
breakage and wear of the wind turbine in service.
Furthermore, the driving of the rotor or of the electric
generators, off one or more turbine rotors, entails the use of
mechanical means which increase the size of the capture units,
particularly in the direction of the axis of rotation of the
turbine rotors and of the generator rotors.
It is therefore preferable to provide a direct connection between
the turbine rotor and the generator rotor. This type of drive
cannot be used in the case of electric generators of current type.
The use of make it possible to make an easier connection with the
turbine rotor of the wind turbine and to increase the compactness
of the capture unit of the wind turbine in the axial direction.
However, such generators of the discoid type have never been used
in wind turbines with contra-rotating turbine rotors.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is therefore to provide a device for
capturing wind energy to produce electrical energy, comprising a
vertical mast, a nacelle mounted so that it can rotate about a
vertical axis on the upper part of the mast and at least one
capture unit comprising at least one turbine rotor consisting of a
hub mounted so that it can rotate on the nacelle about an
approximately horizontal axis and at least two blades fixed to the
hub in approximately radial directions and an electric generator
having at least one rotor connected to the turbine rotor such that
it is driven in rotation by the turbine rotor and at least one
stator fixed to the nacelle, it being possible for this device to
be obtained compactly while at the same time exhibiting high
installed power and making it possible to increase the amount of
energy produced during a reference period, for example over the
course of one year.
To this end, the capture device according to the invention
comprises a first capture unit and a second capture unit, these
respectively comprising a first and a second turbine rotor which
contra-rotate and are arranged one on each side of the vertical
axis of the mast, the hubs of which are mounted to rotate
independently of one another about aligned axes and a first and a
second electric generator produced in discoid shape and each
comprising: at least one rotor having at least one disc-shaped part
secured to the corresponding turbine rotor, at least one stator
having at least one disc-shaped part facing the rotor, and power
electronics means associated with the generator to allow the speed
of the rotor to be regulated independently on each of the capture
units.
The invention also relates to a method for regulating the capture
device in order to optimize its operation so as to produce the
maximum combined energy over a reference period.
In order to make the invention easy to understand, a device for
capturing wind energy and for producing electrical energy according
to the invention and its optimized use for producing a maximum
combined amount of energy over a reference period will now be
described by way of example with reference to the appended
figures.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a view in axial section of the capture device according
to the invention.
FIG. 2 is an enlargement of part of FIG. 1, showing the electric
generator of one of the capture units.
FIG. 3 is a diagram showing, as a function of wind speed, the power
supplied by each of the capture units and the total power supplied
by the device, and the distribution over time of the wind speeds
over a reference period of one year.
FIG. 4 is a diagram showing, as a function of wind speed, the
annual energy production of the capture device according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a capture device according to the invention denoted
overall by the reference 1.
FIG. 1 depicts only the upper part of the mast 2 of the capture
device carrying the nacelle 3 at its upper end, via a bearing 4
which allows the nacelle 3 to be mounted such that it can rotate on
the upper part of the mast 2 about the vertical axis 5.
The mast 2, only the upper part of which has been depicted in FIG.
1, may be very tall, for example of the order of 40 m high, the
lower part of the mast being fixed into a solid footing in the
ground at the wind energy production site.
A streamlined casing 6, of profiled shape, is fitted around the
structure of the nacelle 3. The shape of the streamlining 6 is
chosen, in particular, to meet requirements pertaining to the
visual impact of the wind turbine.
On each side of the vertical axis 5 of the mast 2, about which it
is mounted to rotate, the nacelle 3 has two extensions 3a and 3b,
on each of which is mounted, respectively, via bearings 7a and 7b,
a first hub 8a of a first turbine rotor 10a of the capture device
and a second hub 8b of a second turbine rotor 10b.
The first turbine rotor l0a is for driving the rotor of a first
electric generator 9a, and the second turbine rotor 10b is for
driving the rotor of a second electric generator 9b of the capture
device. The first turbine rotor 10a and the first generator 9a
constitute a first capture and electrical-energy-production unit
and the second turbine rotor 10b and the second generator 9b
constitute a second capture and electrical-energy-production unit
of the capture device 1.
The bearings 7a and 7b for the rotary mounting of the hubs 8a and
8b have an approximately horizontal common axis 11 which is pointed
in the overall direction in which the wind blows while the wind
turbine is in operation. The wind has been depicted in the
conventional way by arrows 13 upstream of the first turbine rotor
10a and 13' upstream of the second turbine rotor 10b.
In general, the turbine rotors 10a and 10b and the generators 9a
and 9b constituting the capture units are mounted on the nacelle 3
in symmetric arrangements with respect to the vertical axis 5 of
the mast 2.
The first turbine rotor 10a is placed facing into the wind depicted
by the arrows 13 and the second turbine rotor 10a is placed on the
lee side of the residual wind which has passed through the first
turbine rotor, this residual wind being depicted by the arrows 13',
the two turbine rotors 10a and 10a being aligned in the direction
of the wind. The turbine rotors 10a and 10b are mounted so that
they can rotate on the nacelle 3, entirely independently of one
another, there being no means of mechanical connection between the
two turbine rotors.
Each of the turbine rotors 10a and 10b consists of the
corresponding hub 8a or 8b and of a set of respective blades 12a or
12b fixed rigidly in approximately radial directions to their hub
8a or 8b.
Each of the rotors may, for example, have two or three radial
blades set 180.degree. or 120.degree. apart about the axis 11 of
rotation of the hubs.
As visible in the central part of FIG. 1, the blades 12a and 12b
have a profiled shape in cross section on a plane parallel to the
axis of rotation of the turbine rotor.
The profiles of the blades 12a and 12b are the reverse of each
other, which means that the wind causes the two turbine rotors to
rotate in opposite directions. The two turbine rotors are therefore
said to be contra-rotatory. The circular arrows 14 and 14' have
been used to, depict the direction of rotation of the first turbine
rotor 10a and of the second turbine rotor 10b, respectively.
Each of the electric generators 9a and 9b is produced in discoid
form and comprises two rotors each of which rotates as one with the
corresponding turbine rotor, and a double stator fixed to part of
the nacelle 3.
The two electric generators 9a and 9b, which are arranged
symmetrically with respect to the axis 5, are produced in the same
way which means that only the generator 9a of the first capture
unit will be described in detail, with reference to FIG. 2.
The generator 9a, produced in discoid form, comprise two stators 15
and 15' of annular overall shape and comprising a part 16 or 16' in
the form of a flat disc carrying, on its external face facing
toward the stator, permanent magnets 17 or 17'. The discs 16 and
16' of the rotors 15 and 15' are secured to an annular hollow rotor
body containing a laminated core consisting of a stack of
laminations. The rotor 15 is fixed directly on the hub 8a by screws
19 which also fix the rotating internal part of the bearing 7a of
the rotary mounting of the hub 8a and of the turbine rotor 10a.
The fixed outer part of the bearing 7a is secured to a part of the
nacelle 3 to which is also fixed the stator 18 of annular overall
shape with two flat discoid faces placed facing flat discoid faces
of the stators 16 and 16' carrying the permanent magnets 17 and
17'.
The two rotors 15 and 15' are secured together by screws which
clamp the discs 16 and 16' of the stators against a multi-part
peripheral ring 20. The rotors are held in the axial direction by
thrust bearings associated with the rotary bearing 7a and by a
double thrust bearing 21 which holds the rotor in the axial
direction and in two opposite directions.
The stator 18 has two parts facing, respectively, the rotor 16 and
the rotor 16' and each of which consists of a laminated core in
which are mounted coils facing the permanent magnets 17 and 17' of
the rotors 16 and 16'.
The coils of the stator 20 are connected by electrical conductors
to means of connecting the generator to a user line for the current
produced. The stator coils are also connected to a box 22 secured
to the nacelle 3 and containing power electronics for controlling
the electric generator and regulating the rotational speed of the
rotors 15 and 15'.
Of course, the second electric generator 9b is connected in the
same way as the first electric generator to power electronics which
may be located in the box 22, so that the first and second electric
generators can be controlled entirely independently and so that the
speed of the rotor of the first generator and of the first turbine
rotor and of the rotor of the second generator and of the second
turbine rotor can be regulated entirely independently.
The method for regulating the capture device according to the
invention by regulating the speed of the rotors of the generators
and of the turbine rotors of the two capture units of the device
according to the invention will now be described with reference to
FIG. 3 and FIG. 4.
FIG. 3 represents, in the form of a curve 23, the number of hours
(along the ordinates axis) in a reference period of one year, for
which the wind to which the capture device according to the
invention is subjected has a speed which is indicated along the
abscissas axis. In reality, each of the points giving a number of
hours with a certain wind speed corresponds to a range of speeds of
an amplitude of one meter/second.
The curve 23 represents the distribution of wind speeds over the
course of the year at the site at which the wind turbine is
erected. The curve 23 has an initial point to the left in FIG. 3,
corresponding to a speed of the order of 3 m/second which is the
wind speed needed to start the wind turbine. The power supplied
respectively by the first capture unit and by the second capture
unit of the device according to the invention, as a function of
wind speed, is also given in FIG. 3, in the form of the curves 24
and 25.
Finally, the curve 26 represents the total power supplied by the
device, that is to say the sum of the powers supplied by the first
and by the second capture units of the device.
As visible in FIG. 3, the two capture units start up at a wind
speed of the order of 3 m/s and the turbine rotors of the capture
units rotate at a speed which increases as the wind speed
increases. Correspondingly, increasing amounts of power are
produced by each of the capture units.
In a first zone A, the speed of the rotary part of the first
capture unit facing into the wind increases until it reaches a
speed that corresponds to the onset of regulation by
aerodynamically stalling the rotary part of the first capture unit.
The speed at which aerodynamic stall begins is around 9 m/second.
This stall may be commanded or obtained automatically when the wind
speed reaches the limit determined by the characteristics of the
first capture unit.
Under the operating conditions in zone A, the first capture unit
works at its maximum efficiency, the coefficient of power CP or
Betz coefficient being at a maximum. The coefficient of power or
Betz coefficient is defined as the ratio of energy recovered to
maximum recoverable energy which represents about 60% of the
kinetic energy of the wind.
Because the first capture unit is operating at maximum efficiency,
the second capture unit has only a fraction of the recoverable
kinetic energy available to drive it, this fraction representing
for example from 50 to 80% of the energy absorbed by the first
capture unit.
FIG. 3 represents the scenario in which the second capture unit has
only 50% of the energy captured by the first capture unit available
to it. The rotational speed of the rotary part of the second
capture unit is adapted to suit the wind speed so that this second
capture unit works at maximum CP coefficient.
In zone A, the total recovered power is, in this instance, equal to
one and a half times the power captured by the first capture unit.
The gain in power due to the second capture unit is therefore, in
this instance, about 50% in zone A.
After zone A, the graph of FIG. 3 represents a zone B ranging from
the point of aerodynamic stall of the first capture unit (for a
wind speed of the order of 9 m/second) up to the point of
aerodynamic stalling of the second capture unit (for a wind speed
of the order of 11 m/second).
In this zone B, the rotary part of the first capture unit begins to
experience aerodynamic stall and the stronger the wind becomes, the
more the rotary part of the first capture unit experiences stall;
what this means is that the residual kinetic energy that can be
recovered by the rotary part of the second capture unit increases
up to the point at which the rotary part of the second capture unit
stalls at a speed (for example 11 m/second) which is dependent upon
the characteristics of the second capture unit. In zone B, the
second capture unit is operating at maximum CP.
In the next zone, C, the two capture units are operating in
conditions of increasing stall, the first capture unit reaching
maximum stalling before the second capture unit which means that
the gain in power contributed by the rotary part of the second
capture unit progresses in zone C from 50%, for the speed at the
onset of stall, to 100% for the wind speed (around about 14
m/second) at which the rotary parts of both capture units are
experiencing aerodynamic stall.
Thereafter, up to the highest wind speeds (zone D), both capture
units are making the same contribution to the total power supplied
by the capture device.
It is therefore obvious that the speed regulation achieved
independently on the rotary parts of each of the capture units
makes it possible, for any wind speed, to optimize the capture
device so that the power supplied by this device will be as high as
possible, given the amount of wind energy that can be
recovered.
The speeds of the rotary parts of the capture units are regulated
by the power electronics associated with the electric generator of
these capture units.
FIG. 4 represents, in the form of a curve 27, the energy produced
in the reference period of one year by the first capture unit as a
function of the wind speed and, in the form of a curve 28, the
energy produced annually by the entire device consisting of the
first and second capture units, as a function of wind speed.
The curves 27 and 28 are obtained from the curve 23 and the curves
24 and 26 respectively, by multiplying the powers supplied by the
number of hours corresponding to that wind speed.
The use of a second capture unit mounted on the nacelle of the wind
turbine after the first capture unit makes it possible to increase
the energy recovery by about 60% to 70% compared with the use of a
single capture unit having a rotary part of the same diameter and
with the same aerodynamic characteristics as the rotary part of the
capture unit used in addition.
Regulating the speed of the rotary parts of the capture units makes
it possible to optimize the recovery of energy on each of the
capture units and, in particular, to make the second capture unit
operate in a way which is optimum for the recovery of the
recoverable energy which is not captured by the first capture
unit.
The device and the method according to the present invention
therefore make it possible to increase the installed power of a
device for capturing wind energy by using a first and a second
capture unit one after the other and to increase the energy
produced over a reference period by regulating the first and second
capture units.
The device according to the invention also is very compact in spite
of the use of two capture units arranged one after the other. This
compactness is obtained by virtue of the use of discoid electric
generators.
Furthermore, the capture device according to the invention has no
complex and fragile mechanical parts and the speed of the rotary
parts of the capture units is regulated entirely by electronic
means.
The invention is not strictly limited to the embodiment which has
been described.
Thus, the turbine rotors and the electric generators of the capture
units may be produced in a different form.
The turbine rotors of the capture units may have any number of
blades, the length of which may be chosen from a vast range.
The electric generator may have one single rotor and one single
stator or, on the other hand, one or more units themselves
comprising one or more rotors and one or more stators.
The power electronics for controlling the electric generators and
regulating the speed of rotors associated with the turbine rotors
may be produced by any means known to those skilled in the art.
The invention applies to the manufacture and operation of any wind
turbine used for producing electrical current.
* * * * *